Hypertension, most commonly referred to as high blood pressure, is a medical condition in which there is an impaired ability of the kidneys to excrete salt and water. As a result of the rise in arterial pressure, the heart must work harder to pump blood through narrowed arteries and can lead to long-term damage to the heart and blood vessels. If this condition persists it increases the risk for stroke, heart attack, kidney disease nd heart failure. It is estimated to cause 1 in every 8 deaths worldwide. In cardiovascular physiology, the baroreflex, or baroreceptor reflex is one of the body's natural mechanisms for maintaining blood pressure. Ultrasound is an ideal energy source for non-invasive stimulation of the baroreceptors because it is does not have ionizing radiation and is low-cost. The goal of this proposal is to demonstrate the potential of using ultrasound as a therapy to treat hypertension by stimulating the carotid baroreceptors. A series of acute studies in a canine model is proposed to identify an appropriate range of stimulation parameters. The following specific aims are proposed to achieve this goal: 1. Design, fabricate, and test needle-shaped transduers operating at 1 MHz for accurate localization of ultrasound onto the carotid sinus, the location of the carotid baroreceptors. 2. Perform 20 acute canine studies to measure the blood pressure (BP) and heart rate (HR) responses to activation of the carotid baroreflex using various ultrasound stimulation parameters. 3. Perform studies in 4 conscious canines to measure the heart rate and blood pressure responses to more prolonged activation of the carotid baroreflex by ultrasound. The ultimate vision of this work is to develop a non-invasive wearable ultrasound therapy device capable of treating patients with treatment-resistant hypertension and possibly other sub-populations of patients suffering from varying degrees of hypertension.